Laser Absorption

Another active diagnostic technique is Laser Absorption. With this technique, not the scattered photons are detected, but the laser beam itself after the plasma is detected to measure the absorption coefficient of the plasma. The absolute value of the absorption coefficient is a direct measurement of the density of the (excited) atomic or molecular state that absorbs the laser radiation can be determined. Absorption techniques can be done with broadband light sources (FTIR), lamps (like a Hg lamp for O3 absorption measurements) and (diode) lasers as for Ar metastable measurements and Dy as has been performed at EPG.